1. Field of the Invention
The present invention relates to a digital-to-analog convertor for a display device and related driving module, and more particularly, to a digital-to-analog convertor with a short response time and related driving module.
2. Description of the Prior Art
A liquid crystal display (LCD) is a flat panel display which has the advantages of low radiation, light weight and low power consumption and is widely used in various information technology (IT) products, such as notebook computers, personal digital assistants (PDA), and mobile phones. An active matrix thin film transistor (TFT) LCD is the most commonly used transistor type in LCD families, especially in the large-size LCD family. A driving system installed in the LCD, includes a timing controller, source drivers and gate drivers. The source and gate drivers respectively control data lines and scan lines, which intersect to form a cell matrix. Each intersection is a cell including crystal display molecules and a TFT. In the driving system (e.g. a driving integrated circuit (IC)), the gate drivers are responsible for transmitting scan signals to gates of TFTs to turn on the TFTs on the panel. The source drivers are responsible for converting digital image data, sent by the timing controller, into analog voltage signals and outputting the voltage signals to sources of the TFTs. When the TFT receives the voltage signals, a corresponding liquid crystal molecule has a terminal whose voltage changes to equalize the drain voltage of the TFT, and thereby changes its own twist angle. The rate that light penetrates the liquid crystal molecule is changed accordingly, and thus different colors can be displayed on the panel.
As technology advances, the resolutions of the liquid crystal display gradually increases (e.g. increases from full high definition (HD) to 4K) and the image quality of the liquid crystal display is also improved. When the resolution of the liquid crystal display increases, charging times of the driving device (e.g. a driving IC), used for driving the display panel in the liquid crystal display, charging the display components in the display panel decrease. On the other hand, the number of bits of color signals requires to be increased in order to improve the image quality of the liquid crystal display. The increase of the number of the bits of the color signals also increases the resistance of a digital-to-analog converting circuit used for converting the color signals to analog voltages, such that the time of the digital-to-analog converting circuit generating the analog voltages according to the color signals is prolonged. Thus, how to decrease the time of the digital-to-analog converting circuit generating the analog voltages to fit the charging time that is decreased when the resolution of the liquid crystal display increases becomes a topic to be discussed.